Between dressing up as Lady Gaga, saving money on catering by using surplus military rations, & crafting a playlist that relies heavily on the Ghostbusters soundtrack, Dean Pelton is certain that he’s put together Greendale’s best Halloween costume party ever. Yet things begin to unravel when Pierce falls ill after feasting on the party’s tacos. Though Rich, a part-time pottery student & classmate of Annie’s who is also a doctor, suspects food poisoning, he’s cautioned by Dean Pelton not to cause a panic. But when a zombie-like Pierce starts biting his classmates on the neck & turning them into zombies, too, the dean & Rich realize they have a bigger problem on their hands.